A boosted engine may operate with intake manifold pressures greater than ambient pressure. An engine may be boosted via a turbocharger or a supercharger. The turbocharger's or supercharger's compressor may pressurize ambient air so that engine output may be increased as compared to if the same engine were constrained to operating at ambient pressure. The engine air flow may increase with increased intake manifold pressure provided by the turbocharger or supercharger compressor. However, if the engine is operated during high humidity conditions, engine output may degrade due to the humidity.
The inventors herein have recognized the above-mentioned issues and have developed an engine operating method, comprising: adjusting an engine air flow threshold via a controller responsive to ambient humidity; and operating an engine responsive to the adjusted engine air flow threshold.
By adjusting an engine air flow threshold in response to ambient humidity, it may be possible to provide the technical result of an engine outputting an equivalent torque output during high humidity conditions as the engine outputs during low humidity conditions. For example, during low humidity conditions, the engine may flow a first air flow amount to provide a maximum torque output at a particular speed. A sensor monitoring the engine air flow may indicate the engine has reached its maximum air flow to provide the maximum torque. However, during high humidity conditions, the same sensor may indicate the engine has reached the first air flow amount without the engine providing the same maximum torque at the same particular speed. The engine torque difference arises due to the sensor not compensating for, but being affected by, the increase in ambient humidity. Nevertheless, the engine torque at high humidity conditions may be restored to the engine torque at low humidity conditions via increasing the engine air flow threshold. Increasing the engine air flow threshold during humid operating conditions causes the engine to induct a same amount of oxygen as if the engine were operated at the same conditions but at a lower humidity and a lower engine air flow threshold. In this way, equal amounts of engine torque may be provided during high and low humidity operating conditions.
The present description may provide several advantages. Specifically, the approach may provide more uniform engine performance over a range of ambient humidity levels. Further, the approach is especially suited for turbocharged engines that have capacity to adjust a maximum engine air flow depending on operating conditions. Further still, the approach may be applied to mass air flow systems and speed density systems.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.